Azimuth ruler



A ril 1 1924. 1,488,899

T. ARIMITSU AZIMUTH RULER Filed March 31 I919 2 Sheets-Shee X aviuewfoz April 1 1624. 1,488,899

T. ARIMIT'SU AZIMUTH RULER 7 Filed March 31 1919 2 SheetS- S het 2 3 mmm .Patented Apr. 1, 1924.

UNITED STATES ATENT iaeaaea F C E TOSHIICHI ARIMITSU, OF YOKO-HAMA, JAPAN, ASSIGNOR TO NIPPON YU'SEN CQ, LTD, 0F TOKYO, JAPAN.

AZIMUTH RULEB.

Application filed March 31, 1919. Serial No. 286,403.

To all whom it may concern:

Be it known that TOSHIIGHI ARIMITSU, subject of the Emperor of Japan, residing at N o. 368 Izumitanito, Kitakatamachi, city of Yokohama, Japan, has invented certain new and useful Improvements in Azimuth Rulers, of which the following is a specification.

This invention relates to apparatus for use in solving nautical problems or plane and spherical trigonometry, mechanically and without the use of logarithmic calculations.

The apparatus according to the present invention consists in the provision of a NE arm and a NW arm arranged perpendicular to one another, an are having its centre at the point of intersection of the inside edges of the said arms and having a scale on its outer edge (graduated 90 degrees), and a scale on the edge of the NE arm having a graduation equal to (OS) the radius of the are as unit length.

The object of this invention is intended not only to solve mechanically the problems in plane and spherical trigonometry with ease and accuracy, without the use of logarithmic calculations or tables, but it is specially. valuable when applied to astronomical navigation, by which the deviation of the compass, alterations in the course of a vessel, or the azimuth of the heavenly body are easily solved.

In the accompanying drawings:

Fig. lshows a plan view of-this invention.

Figs. 2 to 7 show the application of this invention.

This invention consists of three parts, a NE arm (a), a NW arm (6) and an are (0), wherein the two arms NE and NW are perpendiculars and the arc is fitted so as to have its centre 0 at the point of intersection of the inside edges of the arms.

The standard size is 18 inches for the NE arm, 8 inches for the NW arm, and 6 inches in radius for the arm for all practical purposes. It is to be understood however, that these sizes can be varied, if desired.

The special feature of this invention is the combination of the angular graduation on the arc and the scale on the NE arm which graduation is made with the radius of the are as unit of length, the point of unit,

If the instrument is made of transparent substances, the scale and the graduation are arranged under the surface of the instrunent, for reducing the parallax of the reading-to a minimum.

If however the instrument is made of metallic substances, the graduations are arranged on the surface, and the method of minimizing the parallax of the-reading is t3 bevel a partof the graduation to a knife e ge.

The method of using the apparatus will now be explained with reference to Figures In these figures M and L represent perpendiculars on the Mercators chart, L being the parallel of latitude and M meridian.

In order to commence calculations the apparatus as illustrated in Figure 2 is placed on the chart, so that the parallel of latitude L will make tangent with the arc and the centre of the arcO will coincide with the line of meridian M.

This relative position of the apparatus with the cross lines M and L is called tangent form which is one of two fundamental forms from which nautical calculations are started.

These two fundamental forms are known as tangent form and sine form, I the latter being classified into No. 1 sine form and No. 2 sine form.

The cross lines M and L with the apparatus at the position known as tangent form as shown in Figure 2 will make two right angled triangles, the several sides of. which represent the trigonometricalfunctions of tan (tangent) cot (cotangent), sec (secant), cosec (cosecant).

According to Figure 3 the apparatus is placed on the chart so that the point S 00- incides with the line of latitude L and the centre of the are 0 with the line of meridian M.

This relative position of the apparatus with the lines M and L describes the other fundamental form from which calculations are started and which is known by the name of sine form.

The cross lines M and L at this position form a right angled triangle and each side will represent the trigonometrical function of sine and cosineas shown in Figure 3.

In order to use the apparatus for solving the line of problems in nautical astronomysuch as finding the azimuth of a heavenly body and thence the deviation of the compass, there are several kinds of motions which are started from one of the above mentioned fundamental forms. A motion which is started from tangent form i called tan motion and relates to a motion of the apparatus in which the centre of the are 0 slides along the line of meridian M, keeping the length of the'tangent a lined quantity, as shown in Figure A motion which is started from sine form is called sine motion and relates to a motion of the apparatus in which the centre of the are 0 slides along the line M, keeping the length of the sine a constant quantity as shown in Figure 6. Slide motion is one wherein a fixed length is taken on the scale such as O R, 0 being the centre of the arc sliding on the line M and R a point on the NE arm sliding along the line L. For every position, therefore, of the apparatus with respect to the cross lines M and L the length 0 R will be constant, that is to say OR O, R. r

The motion, in No. 2 sine form i turned into a turning motion and is called sine turning motion. In this motion the apparatus is placed in position with relation to the cross lines as shown in Figure l, the centre of the are 0 coinciding with the line M. The apparatus is turned about the point 0 keeping the length M a constant quantity as shown in Figure 7. V l

An example will now be given showing the method of solving nautical formula by the use of this device.

Example 1.

tan L. cotoHi A.

Where Lzlatitude. Hzho-ur angle.

Place the instrument in the position shown in dotted lines in Fig. 5, placing the junction of the two arms on the meridian line M and arranging the arm aso that the graduation on that arm corresponding to the latitude given is intersected by the parallel L.

Mark the point of this intersection and then move the instrument in such manner that the intersection of the two arms follow EmampZc 2. sin H. 'cosec. 2. cos. dzsin. A2

where Ell-hour angle. 7 Zzzenith distance. dzdeclination.

v rizzazimuth.

Place the instrument, as shown inFig. 3, so that the intersection of the two arms co: incides with the meridian line M, the intersection of the end of the are c with the arm a coincides with the parallel of latitude L, and the-meridian line M cuts the sour angle given as read on the arc 0. Now more the instrument through the sine motion until the meridian line intersects the are c on the Zenith distance, and read on the scale 01 the arm (a the distance between the intersection of the arms and the parallel of latitude calling this m. With this value as a constant, rotate the instrument on the center of the are 0 until the position previously de scribed asllo. 2 sine form has been obtained. Then the azimuth maybe read directly on the are c.

I claim- Apparatus for use in solving nautical problems or plane and spherical trigonometry comprising arms arranged perpendicular to one another, an are having its centre at the point of intersection of the inside edges of the said arms and having a scale on its outer edge graduated 90 degrees and a scale on the edge of one arm having a graduation equal to the radius o1 the are as unit of length. V

In testimony whereof he 'afiixes his signature in the presence of two witnesses.-

TOSHHIi-li ARIM TESL. in. s] Witnesses 5. Bones Fnnsan, G'EUJI KUREBANA,

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